WST-8

WST-8 (CAS No.: 193149-74-5) is a water-soluble tetrazolium salt widely employed as a sensitive colorimetric reagent for assessing cellular metabolic activity and viability in biomedical research and drug discovery. Functionally, WST-8 serves as a redox indicator that is reduced by NADPH-dependent cellular oxidoreductases associated with plasma membrane electron transport systems, particularly in metabolically active cells, in the presence of an intermediate electron acceptor such as 1-methoxy phenazine methosulfate. This enzymatic reduction generates a water-soluble orange formazan product with a characteristic absorbance around 460 nm, and the quantity of this product is directly proportional to the number of viable cells. Compared with traditional tetrazolium-based assays such as MTT or MTS, WST-8 offers enhanced sensitivity and operational convenience by eliminating the need for additional solubilization or cell lysis steps, thereby enabling more streamlined and reproducible workflows. Although not acting on a single defined molecular target, its mechanism reflects integrated cellular redox and metabolic activity, making it a robust surrogate marker for cell viability and proliferation. WST-8-based assays are extensively utilized in vitro for high-throughput screening of cytotoxic agents, evaluation of drug sensitivity, and monitoring of cell proliferation across diverse cell models, with experimental concentrations typically optimized according to assay format and cell type.